Just as macOS’ versatility allows iOS to remain lightweight, the
ability of the rest of the Mac lineup to be more aggressive,
minimalist, and forward-looking depends on the Mac Pro to cover
everyone whose needs don’t fit into them. The Mac Pro must be the
catch-all at the high end: anytime someone says the iMac or
MacBook Pro isn’t something enough for them, the solution should
be the Mac Pro.

Here’s the short version of the “Mac is doomed” scenario: iOS is
the future, Mac OS X is the past, and Apple is strongly inclined
to abandon the past in the name of the future.

You can’t really argue with that, can you? But the premise that
the end is near for the Mac presupposes quite a bit about the
near-term future of iOS.

[…]

At typical companies, “legacy” technology is something you figure
out how to carry forward. At Apple, legacy technology is something
you figure out how to get rid of. The question isn’t whether iOS
has a brighter future than the Mac. There is no doubt: it does.
The question is whether the Mac has become “legacy.” Is the Mac
slowing iOS down or in any way holding it back